A nephelometric turbidimeter determines the concentration of solid particles suspended in a liquid sample within a sample cuvette by projecting a measurement light beam into the liquid sample within the cuvette. An optical turbidity sensor provided outside the cuvette body detects the amount of light scattered by the suspended solid particles at an angle of typically 90° with respect to the light beam axis.
If condensate exists at the outside surface of the cuvette body, the light signal received by the measurement sensor is scattered by the condensation on the cuvette body so that the true turbidity of the liquid sample cannot be determined. The condensate at the cuvette body can also result in water drops dropping downwards from the cuvette body which causes optical and/or electronic disturbances and damage at the optics and/or electronics of the turbidimeter.
Condensation on the outside of the cuvette body and on the other parts of the turbidimeter in particular appears if the liquid sample is colder than the air in the cuvette chamber in which the cuvette is arranged during the turbidity measurement process, and if the relative humidity of the air inside the cuvette chamber is high. Condensation can be avoided by heating the cuvette chamber via a heating device which, however, results in a high consumption of electrical energy.